Formation and reactivity of a transient cationic alkyl phosphinidene complex

Reaction of the chloroisopropylphosphido complex [Cp*Mo(CO) ₃{P(Cl)i-Pr}] (1) with AlCl₃ generates the transient cationic alkylphosphinidene complex [Cp*Mo(CO)₃ {P(i-Pr)}][AlCl₄] (2). If it is generated in the presence of diphenylacetylene, 2 undergoes a (1 + 2) cycloaddition to form the phosphirene complex [Cp*Mo(CO)₃{P(i-Pr)C(Ph)C- (Ph)}][AlCl₄] (3). Reaction of 2 with PPh₃ forms the phosphine- coordinated phosphinidene complex [Cp*Mo(CO)₃{P(PPh₃)(i-Pr)}] [AlCl₄] (4). Compound 2 reacts with Ph₂SiH₂ to insert the phosphinidene phosphorus atom into the Si-H bond, forming the secondary silylphosphine complex [Cp*Mo(CO)₃ {P(H)(SiHPh ₂)(i-Pr)}][AlCl₄] (5). Similarly, 2 reacts with ferrocene to activate a C-H bond, resulting in the formation of [Cp*Mo(CO) ₃{P(H)(i-Pr)(C₅H₄FeC₅H ₅)}][AlCl₄] (6).